Sexual Dimorphism in c-Fos Networks Governing Aggression.

Circuit based studies of aggression often focus on the activity of a small group of regions referred to as the "core aggression circuit," yet a whole-brain map of activity has yet to be produced. Using resident-intruder assays in male and female Swiss Webster mice, we combined iDISCO+ c-Fos imaging with a weighted co-expression network analyses to identify mesoscale co-activation modules in aggressive (AGG) and non-aggressive (NON) animals. We performed a module preservation analysis between each phenotype within each sex followed by differential correlation to localize edge-level changes. Behaviorally, AGG mice spent more time attacking, while females showed greater social investigation. When comparing activity changes in individual regions, male AGGs showed broad activation throughout the anteroposterior axis, while females preferentially activated anterior cortical regions. Network analyses revealed that NON networks often preserved density of AGG modules, but connectivity reorganized with aggression. In male AGGs there was large spread reorganization of numerous modules: a large sensorimotor-subcortical "blue" module, a pallidal/hypothalamic/brainstem "yellow" module, and a brainstem-heavy "green" module. Surprisingly the "brown" module, enriched for classic social-behavior regions was moderately preserved in male NONs. In females, the "turquoise" module spanning somatosensory/interoceptive cortex and midbrain regions and the "red" module spanning many anterior cortical and thalamic regions were the least preserved. These results indicate that aggression recruits distributed mesoscale communities via edge-specific gain, with males displaying broad strengthening throughout the brain and females showing more targeted potentiation within anterior cortical modules. This framework nominates candidate hubs and edges for causal manipulation.